Lactic Acid Polymer Research Articles

The use of alkali treated walnut shells as filler in plasticized poly(lactic acid) matrix composites

Different amounts of walnut shell flour have been added to poly(lactic acid) polymer plasticized with 10 wt% epoxidized linseed oil to prepare biocomposites. The novelty of this work is the preparation and characterization of biocomposites based on alkali treated walnut shell flour and plasticized PLA matrix. Alkali treatment removed the major part of non-cellulosic components of walnut shell improving the thermal stability and crystallinity index. Furthermore, alkali treatment improved the adhesion between walnut shell and plasticized PLA matrix and consequently, the tensile strength value of composite improved around 50 %, compared with untreated counterpart. Nevertheless, the tensile strength and Young´s modulus values of biocomposites with treated walnut shell were similar to unfilled blend and maintained almost constant irrespective to the filler content. Despite the elongation at break decreased after the addition of walnut shell, the prepared biocomposites showed similar ductility to non-plasticized PLA polymer.

Macrocycle-based oligo- and polylactides: synthesis and prospects of application

The review considers methods for modifying oligo- and polymers of lactic acid by macrocyclic moieties (cyclodextrin, tetrapyrrole, and calixarene) and the effect of modifiers on the complexing, thermal, and aggregation properties. Analytical characteristics of oligolactide-based sensors and biosensors are discussed, with particular emphasis on the mechanism of signal generation and the contribution of modified materials to the selectivity and sensitivity of analysis.

Functionalized starch microparticles for contact-active antimicrobial polymer surfaces

Starch is an attractive biomacromolecule for functional materials due to its renewability, biodegradability, amenability for modification, and biocompatibility in mammalian cell lines. In this research, starch was proposed as a modular platform to produce antimicrobial polymer surfaces. Conjugation of biocidal molecules via chemical grafting onto starch (starch-g-biocide) and its antimicrobial properties in poly (lactic acid) (PLA) polymers were investigated. Polyhexamethylene guanidine hydrochloride (PHGH) was synthesized and used as an antimicrobial agent. The grafting was confirmed by FTIR, proton NMR, and elemental analysis. The modified starch was then incorporated into the PLA films at various concentrations, and the antimicrobial efficacy of these films were evaluated against a Gram-positive bacterium, Bacillus subtilis and a Gram-negative bacterium, Escherichia coli. The results showed that the polymer surfaces have high antimicrobial potency when bacteria contact them. This material therefore has great potential for self-decontaminating surfaces, such as medical devices and food packaging applications.

Promotion through external magnetic field of osteogenic differentiation potential in adipose-derived mesenchymal stem cells: Design of polyurethane/poly(lactic) acid sponges doped with iron oxide nanoparticles.

Recently, iron oxide nanoparticles (IONPs) have gathered special attention in regenerative medicine. Owing to their magnetic and bioactive properties, IONPs are utilized in the fabrication of novel biomaterials. Yet, there was no report regarding thermoplastic polyurethane (TPU) and poly(lactic acid) (PLA) polymer doped with IONPs on osteogenic differentiation of mesenchymal stem cells. Thus the objectives of presented study was to: (a) fabricate magnetic TPU + PLA sponges doped with iron (III) oxide Fe2 O3 nanoparticles; (b) investigate the effects of biomaterial and its exposition to static magnetic field (MF) on osteogenic differentiation, proliferation, and apoptosis in adipose-derived mesenchymal stem cells (ASCs). TPU + PLA sponges were prepared using solvent casting technique while incorporation of the Fe2 O3 nanoparticles was performed with solution cast method. RT-PCR was applied to evaluate expression of osteogenic-related genes and integrin's in cells cultured on fabricated materials with or without the stimulation of static MF. MF stimulation enhanced the expression of osteopontin and collagen type I while decreased expression of bone morphogenetic protein 2 in tested magnetic materials-TPU + PLA/1% Fe2 O3 and TPU + PLA/5% Fe2 O3 . Therefore, TPU + PLA sponges doped with IONPs and exposure to MF resulted in improved osteogenic differentiation of ASC.

Recent advancement in wound healing dressing material

Wounds have been occurring as long as the existence of life. Presently available advanced wound care products for dressing are beyond the reach of the majority Indian population, and they also do not completely fulfil the required benefits of therapeutic value. The dermal patch technology is the best-known and widely used approach for delivering drugs. It has been proven to be the fastest, easiest, safest and most economical way for drug delivery. The use of biodegradable polymers in wound management has been brought into prominence with new innovations in drug delivery system. Thus with a new dimension for the use of polymeric materials in or as wound healing, drug delivery devices involves incorporation of biodegradability into the drug delivery system. A number of degradable polymers are potentially useful for drug delivery including a variety of synthetic and natural substances such as Poly Lactic acid, Poly Crypolactone, Chitosen etc. Among all these Poly (lactic acid) (PLA) is the most readily biodegradable polymer in the surgical field. The biodegradable polymers have gained growing importance in the medical area, and these have been used in a wide number of applications in the human body, such as surgical sutures, controlled drug release systems, artificial skins, guides for nerves, veins and artificial arteries and orthopaedic devices. Biodegradable polymers have several physical and chemical characteristics, such as molecular mass average and distribution, glass transition and/or melting temperatures, monomer ratios and sequencing for copolymers. The knowledge of physicochemical characteristics of Poly Lactic acid polymers essential to understand its thermo-mechanical performance. In order to achieve appropriate wound healing, sustained release of the drug from the bio-degradable patch is necessary. So the assessment of the interaction between the drug and polymer is indispensable.

Sustained Release of Hydrogen Sulfide (H2S) from Poly(Lactic Acid) Functionalized 4-Hydroxythiobenzamide Microparticles to Protect Against Oxidative Damage.

Hydrogen sulfide (H2S) has emerged as a gaseous mediator capable of exhibiting many beneficial properties including cytoprotection, anti-inflammation, and vasodilation. The study presented here provides characterization of a poly(lactic acid) polymer with a functionalized 4-hydroxythiobenzamide (PLA-4HTB) capable of extended H2S release. The polymer was used to fabricate microparticles that can be potentially loaded with a drug allowing for co-release of the drug and H2S. Microparticles with the average diameter of 500 ± 207 nm were fabricated and shown to release 77.0 ± 1.76 µM of H2S over 4 weeks (release of H2S from 1 mg of particles). To test for the antioxidant properties of the PLA-4HTB microparticles, human embryonic kidney 293 cells were first incubated with PLA-4HTB microparticles and then oxidative stress was induced using CoCl2. Particle suspensions of 1 mg/mL were shown to protect cells resulting in reactive oxygen species (ROS) levels of superoxide that were similar to that of the control group. The microparticles fabricated from the PLA-4HTB released H2S over a sustained period of weeks to months, while providing protection from ROS. The microparticles described in this article represent a new platform technology that could be used to prevent and treat diseases caused by oxidative damage.

Preparation, characterization and evaluation of cellulose nanocrystal/poly(lactic acid) in situ nanocomposite scaffolds for tissue engineering

Cellulose nanocrystal (CNC)/poly(lactic acid) (PLA) in situ nanocomposite scaffolds were fabricated by in situ polymerization of lactic acid and CNC which was directly utilized as aqueous suspension, followed by a process of thermally induced phase separation. The CNC/PLA in situ nanocomposite porous scaffolds were characterized by mechanical test, protein adsorption, hemolysis test, in vitro degradation measurement, TEM, FTIR, SEM and WAXD. Compared to the PLA scaffold, the CNC/PLA in situ nanocomposite scaffolds showed a greatly increased compression modulus, an improved hemocompatibility and protein adsorption capacity. The inclusion of CNCs boosted the in vitro degradation of the in situ nanocomposite porous scaffolds and facilitated the deposition of Ca2+, CO32−, PO43− ions in simulated body fluid. Furthermore, cell cultures were carried out on the CNC/PLA in situ nanocomposite porous scaffolds. In comparison with the PLA scaffold, the in situ nanocomposite scaffolds improved cell attachment and enhanced cell proliferation, denoting low cytotoxicity and good cytocompatibility. It can therefore be concluded that such scaffolds with excellent mechanical property, biocompatibility, biomineralization capacity and bioactivity hold great potential for bone tissue engineering.

Towards sustainability of lactic acid and poly-lactic acid polymers production

Lactic acid (LA) is a platform chemical which can be produced biotechnologically on agricultural residues, wastes and by-products and further used for production of biodegradable, biocompatible LA polymers. These polymers are mostly used for high-end applications but they have potential for much wider application with decrease in production costs. Available technologies and strategies are reviewed in order to point out the issues, challenges and solutions relevant to increase sustainability and competitiveness of LA production on agricultural residues and wastes. Data on chemical composition, regional and seasonal availability of agricultural residues, wastes and by-products are lacking to provide predictable and effective combining for LA production. Precision agriculture, remote sensing and integration with data on chemical composition can help in better planning and more adequate exploitation of available sources in future. Novel pretreatments for the most abundant lignocellulosic feedstocks, which allow utilization of carbohydrates in LA production and side streams like lignin in other biorefineries are needed. Integration of pretreatment, hydrolysis and fermentation under non-sterile conditions or open fermentation mode should enable easier scale up and decrease energy consumption and costs without sacrificing LA purity. Capital investments in improvement of the available technologies are high. Support from policy makers stimulating production of LA polymers from second and third generation feedstocks will help in research, development and faster adoption on larger scale. For production of LA polymers with tailored properties, it is essential to choose the most productive method for LA production and separation from these complex substrates. The shift in research interest from LA polymerization towards “green” processing of LA polymers products is occurring and that will be the additional driving force for the field in future.

Poly(lactic acid) composite films reinforced with microcrystalline cellulose and keratin from chicken feather fiber in 1‐butyl‐3‐methylimidazolium chloride

ABSTRACTAmphiphilic keratin from chicken feather fiber (CFF) and hydrophilic cellulose were incorporated as fillers into hydrophobic poly(lactic acid) (PLA) polymer blend. This study implemented ionic liquid (IL) of 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) to dissolve the 1 wt % fillers. The composite films were compared with and without the addition of IL prepared from five sets of ratios of CFF to MCC using measuring mixers and compression molding. Thermal analysis showed that increase in CFF composition decreases the glass‐transition temperature (T g), and crystallization temperature (T c) as well as increases the degree of crystallinity. PLA composite with the 70/30 ratio of CFF to MCC was found to be the optimum composition in obtaining considerably low T g and high crystallinity. BMIMCl enhanced the miscibility of the composites as observed in scanning electron microscope images and single T g. Apart from creating porous structure and lowering mechanical hardness, BMIMCl also decreased the thermal stability of the PLA composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47642.

Enhanced biosorption and electrochemical performance of sugarcane bagasse derived a polylactic acid-graphene oxide-CeO2 composite

Abstract In view of the methyl orange (MO) dye on everyday applications in the textile, food, leather, paper, printing, and pharmaceuticals industry, in addition to its toxic behaviour on human health, we have developed a biodegradable polylactic acid (PLA)-based cerium dioxide (CeO2)-graphene oxide (GO) composite by means of a sol-gel technique and tested its efficacy. For the study, the PLA polymer obtained is of renewable agriculture waste origin (sugarcane bagasse) and was isolated by means of fermentation of the feedstock followed by the polymerization of lactic acid. The instrumental techniques such as the powdered x-ray diffraction, scanning electron microscopy etc. were employed for the physical characterization of the material. The various parameters such as the kinetics, desorption, regeneration, pH, isotherm theories, and ionic strength were tested towards the adsorption of MO dye onto the surface of GO-PLA-CeO2 composite. The outcome of the study exhibited that the GO-PLA-CeO2 composite revealed promising behaviour for the dye removal, which was allocated to the efficacy of GO, PLA, and CeO2 properties. Also, the adsorption process of GO-PLA-CeO2 is completely dependent on the initial concentration of MO and the adsorption equilibrium fitted well with the Langmuir isotherm. In addition, the electrochemical characterization of the composite was studied by means of CV and impedance measurements. Based on the outcome of the results, it can be said that the GO-PLA-CeO2 composite may be applied as a suitable electrode material along with its efficient adsorption properties for the removal of MO dye from wastewater.

Elucidating the dechlorination mechanism of hexachloroethane by Pd-doped zerovalent iron microparticles in dissolved lactic acid polymers using chromatography and indirect monitoring of iron corrosion.

The degradation mechanism of the pollutant hexachloroethane (HCA) by a suspension of Pd-doped zerovalent iron microparticles (Pd-mZVI) in dissolved lactic acid polymers and oligomers (referred to as PLA) was investigated using gas chromatography and the indirect monitoring of iron corrosion by continuous measurements of pH, oxidation-reduction potential (ORP), and conductivity. The first experiments took place in the absence of HCA, to understand the evolution of the Pd-mZVI/PLA/H2O system. This showed that the evolution of pH, ORP, and conductivity is related to changes in solution chemistry due to iron corrosion and that the system is initially cathodically controlled by H+ mass transport to Pd surfaces because of the presence of an extensive PLA layer. We then investigated the effects of Pd-mZVI particles, temperature, initial HCA concentration, and PLA content on the Pd-mZVI/PLA/HCA/H2O system, to obtain a better understanding of the degradation mechanism. In all cases, HCA dechlorination first requires the production of atomic hydrogen H*-involving the accumulation of tetrachloroethylene (PCE) as an intermediate-before its subsequent reduction to non-chlorinated C2 and C4 compounds. The ratio between Pd-mZVI dosage, initial HCA concentration, and PLA content affects the rate of H* generation as well as the rate-determining step of the process. A pseudo-first-order equation can be applied when Pd-mZVI dosage is much higher than the theoretical stoichiometry (600mg for [HCA]0 = 5-20mgL-1). Our results indicate that the HCA degradation mechanism includes mass transfer, sorption, surface reaction with H*, and desorption of the product.

Use of microperlite in direct polymerization of lactic acid

PLA is one of the most frequently used biodegradable polymers. In this work, PLA was synthesized by direct condensation polymerization of lactic acid in the presence of microperlite to obtain enhanced thermal stability of PLA polymer. Molecular weights of the synthesized polymers were determined by GPC. Chemical structure analyses was done by FTIR. The degree of crystallinity was evaluated by DSC and XRD. Thermal stability of polymers was investigated by DSC and TGA. It has been observed that the existence of perlite has significantly increased the crystallinity and degradation temperature, therefore, enhanced the thermal stability of the PLA.

Facile catalytic ring opening polymerization of lactic acid: Comparing the performance of Fe and Zn metal species

As a bio‐compatible/degradable polymer, poly(lactic acid) (PLA) has been widely noticed in tissue engineering and medical applications. Proper catalytic ring‐opening polymerization of lactic acid is pertinent to development of active metal species capable of producing high‐molecular‐weight polymers. In this work, ligand catalyst (2,4‐di‐tertio‐butyl‐6‐{[(2‐di‐methyl‐amino ethyl) methyl amino] methyl} phenol) was synthesized and then attached to Fe‐based and Zn‐based metal substitutes, and performance of metal species toward ring opening polymerization of lactic acid has been investigated. Regulation of reaction condition at 180°C for 36 h with Zn‐based catalyst allowed for late‐stage production of a high‐molecular‐weight PLA, while Fe‐based facilitated polymerization at early stages leading to PLAs with comparatively twofold higher molecular weight at lower time, monomer‐to‐initiator ratio, and temperature (at 170°C). A ratio of monomer to initiator of 5000 with Fe catalyst resulted in the highest molecular weight. Thus, polymerization has been facilitated by the use of Fe‐based catalyst. For this class of catalyst with Fe substitute, the product was characterized by means of 1H‐NMR, Fourier transform infrared spectroscopy, and differential scanning calorimetry analyses. J. VINYL ADDIT. TECHNOL., 25:215–224, 2019. © 2018 Society of Plastics Engineers

Tunable mesoporous films from copolymers with degradable side chains as membrane precursors

Membrane-based separations have shown promise for a host of applications. Yet, the development of polymer materials suitable for the preparation of membranes with tunable pore sizes between 2 and 10 nm remains challenging. In this study, we utilized poly[styrene-co-oligo(lactide) methacrylate] copolymers containing equal mass fractions of styrene and oligo(lactide) methacrylate as membrane precursors. The side chain of the oligo(lactide) methacrylate served as a sacrificial pore template, and by controlling the degree of lactic acid polymerization, n, between n = 21 and n = 40 the size of the pore templating domains could be tuned. After films were treated with a basic NaOH solution to hydrolyze the oligo(lactide) side chains, the porous films had well-defined pore sizes despite evidence of pore collapse. Poly(ethylene oxide) was filtered from methanol based on molecular size. Furthermore, we demonstrated that pore-solute interactions play a significant role in membrane performance and can lead to the selective removal or enrichment of solutes that possess characteristic dimensions several times smaller than the pore size of the membrane. Specifically, using a membrane with a pore diameter of 16 nm, Naphthol Yellow S (358 g mol−1) was rejected ~62% due to electrostatic repulsion and Martius Yellow (234 g mol−1) was enriched 4-fold due to hydrogen bonding between the solute and membrane pore.

Influence of PLA Filament Conditions on Characteristics of FDM Parts.

Additive manufacturing technologies play an important role in Industry 4.0. One of the most prevalent processes is fused deposition modelling (FDM) due to its versatility and low cost. However, there is still a lack of standardization of materials and procedures within this technology. This work aims to study the relationship of certain operating parameters and the conditions of poly(lactic acid) (PLA) polymer with the results of the manufactured parts in dimensional terms, surface quality, and mechanical strength. In this way, the impact of some material characteristics is analyzed, such as the pigmentation of the material and the environmental humidity where it has been stored. The manufacturing parameter that relates to these properties has been the extrusion temperature since it is the most influential in this technology. The results are quite affected especially by humidity, being a parameter little studied in the literature.

Preparation of bergenin - Poly (lactic acid) polymers and in vitro controlled release studies

The efficacy of bergenin prepared with osmotic-pump-controlled release is much lower than expected. In this study, biodegradable polylactic acid is used to modify bergenin and immobilize it with chemical methods. Bergenin-PLA obtained by this method has low molecular weight and good thermal stability, as well as prolonged in vitro release time along with increased molecular weight. Biocompatibility tests and in vitro antitumor tests showed that bergenin-PLA at a ratio of 1:30 has good biological properties and low cytotoxicity at t three concentrations, and its antitumor activity was significantly increased compared to bergenin. The chemical immobilization of bergenin not only provides a good mode of administration for patients but also provides a good foundation for the sustained release of drugs over time.

443 An Evaluation of Patients that Failed Outpatient Management but Rescued by the Use of Synthetic Lactic Acid Polymer

443 An Evaluation of Patients that Failed Outpatient Management but Rescued by the Use of Synthetic Lactic Acid Polymer

Effect of different carbon sources on denitrification performance, microbial community structure and denitrification genes

Solid and liquid organic substances as carbon sources for denitrification process were deeply explored. In this study, the effect of three carbon sources, referred to as poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/poly (lactic acid) (PHBV/PLA) polymer, glucose and CH3COONa, on denitrification performance, microbial community and functional genes were investigated. It was found that maximum denitrification rates of 0.37, 0.46 and 0.39gN/(L·d) were achieved in PHBV/PLA, glucose and CH3COONa supported denitrification systems, respectively. Meanwhile, Illumina MiSeq sequencing revealed that three carbon sources led to different microbial community structures. It can be seen that Brevinema/Thauera/Dechloromonas, Tolumonas/Thauera/Dechloromonas, Thauera dominated in the PHBV/PLA, glucose and CH3COONa supported denitrification systems, respectively. Transcriptome-based analysis further indicated that the glucose supported denitrification system showed the highest FPKM values (the fragments per kilobase per million mapped reads) of the genes participating in the dissimilatory nitrate reduction process, corresponding to the greatest effluent NH4+-N concentration. A better knowledge of effect of different carbon sources on denitrification process will be significant for nitrate removal in practice.

Nondestructive Evaluation and Detection of Defects in 3D Printed Materials Using the Optical Properties of Gold Nanoparticles

Three-dimensional (3D) printing techniques are being rapidly adopted for prototyping and product development across fields as scientifically diverse as wind energy and regenerative medicine. Through materials processing advancements, the incorporation of nanomaterials within 3D printed parts and structures has begun to enable enhanced material functionalities. In this work, the optical properties of gold nanoparticles are harnessed via the development of functionalized printer filament to detect defects and missing print layers in 3D printed parts. Gold nanoparticles are incorporated within a poly(lactic acid) polymer host matrix, and filament compatible with stock 3D printers is fabricated. Consistent with Beer–Lambert’s Law for nanoparticles in solution, a linear relationship between absorbance intensity and the total number of print layers is observed. By analyzing changes in absorbance intensity, the presence, location, and extent of material defects as small as 0.2 mm are identified through a nondest...

3D 프린터 필라멘트 제작용 대나무/PLA 바이오복합재료 개발 연구

In this study, the 3D printer filaments were manufactured by using the representative eco-friendly material, bio-composite. Bio-composites were made by incorporating biodegradable polymer of poly lactic acid (PLA) as the matrix and bamboo flour as the filler. The bamboos which were used in this experiment are Phyllostachys bambusoides, Phyllostachys nigra var. henonis, and Phyllostachys pubescen grown in Damyang district in Korea, and the mixture ratio between bamboo flour and PLA were set 10/90, 20/80, 30/70 by weight standard. Also, tensile strength of bamboo/PLA bio-composites manufactured with three kinds of bamboo were estimated and compared. In this result, the highest estimated bio-composites was Phyllostachys bambusoides flour/PLA which mixture ratio was 10/90, that is, it was the most suitable bamboo/PLA bio-composites for manufacturing 3D printer filament.